Secondary batteries which are highly applicable to various products and exhibit superior electrical properties such as high energy density, etc. are commonly used not only in portable devices but also in electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by electrical power sources. The secondary battery is drawing attentions as a new energy source for enhancing environment friendliness and energy efficiency in that the use of fossil fuels can be reduced greatly and no byproduct is generated during energy consumption.
Secondary batteries widely used at the preset include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries and the like. An operating voltage of the unit secondary battery cell, namely a unit battery cell, is about 2.5V to 4.2V. Therefore, if a higher output voltage is required, a plurality of battery cells may be connected in series to configure a battery pack. In addition, depending on the charge/discharge capacity required for the battery pack, a plurality of battery cells may be connected in parallel to configure a battery pack. Thus, the number of battery cells included in the battery pack may be variously set according to the required output voltage or the demanded charge/discharge capacity.
Here, the battery module includes a module case in which battery cells and various electrical parts are packaged, and a module connector connected to an external connector for electrical connection with an external device outside the module case. The external connector may be, for example, a connector for electrically connecting a plurality of battery modules. Here, the battery pack including at least one battery module is used for household purposes or industrial purposes depending on various voltage and capacity requirements, and battery racks respectively including at least one battery pack may be combined to configure an energy storage system.
A conventional energy storage system includes at least one battery rack having at least one battery pack, at least one rack housing having an accommodation space for accommodating at least one battery rack, and a rack door mounted to at least one rack housing to open or close the accommodation space of at least one rack housing. Here, the rack door is generally made of steel material and mounted to the rack housing.
However, due to the weight of the rack door made of steel material, the entire weight of the conventional energy storage system is increased, which may cause a problem in reducing the product weight in the recent slimming trend.
In addition, in the conventional energy storage system, the rack door is shaped to have a mesh structure or the like for the circulation of inside air, but the cost for this shaping process is inevitably increased due to the steel material.
Therefore, there is a need to find a method of providing an energy storage system capable of reducing the manufacturing cost while decreasing the weight of the product.